Conventional film/screen radiography uses radiographic films which are not reusable. Computed radiography solves this problem by using reusable storage phosphors that can be exposed, read out, erased and reused many times. In order to protect the storage phosphor from damage during use, it is contained in a cassette from which it is removed during the reading and erasing process. One type of storage phosphor reader receives cassettes, one at a time, oriented horizontally. The cassette containing an exposed storage phosphor is presented to the reader horizontally, the storage phosphor is removed from the cassette and moved along a horizontal path, where it is read and then erased before the storage phosphor is replaced in its cassette. The cassette is then removed and a new cassette manually presented to the reader. In order to increase storage phosphor reader throughput and to relieve the reader user of sequentially loading and unloading storage phosphor cassettes, a multi-cassette autoloader was developed (See: U.S. Pat. No. 5,324,957, issued Jun. 28, 1994, inventor Hejazi). The autoloader disclosed in the latter patent is a separate piece of equipment from the storage phosphor reader and utilizes cog belts to index a plurality of horizontally oriented cassettes to a read site where the storage phosphors are removed from the cassettes and transported into and out of the storage phosphor reader. Because the cog belts are designed to accept only one size of cassette, the largest, and because many sized cassettes are used in the medical imaging field, pallets are used to handle smaller sized cassettes.
Although the latter autoloader is useful and successful for its intended purposes, it has certain drawbacks. Because the autoloader is a separate piece of equipment, substantial floor space is required to accommodate both the reader and the autoloader. Moreover, the use of pallets requires additional manual operations for the operator and creates storage problems when the pallets are not being utilized. A more compact storage phosphor reader is disclosed in U.S. Pat. No. 6,437,359 B1, issued Aug. 20, 2002, inventors Hall et al. As disclosed in the latter patent, the storage phosphor reader receives a storage phosphor cassette in a vertical orientation, removes the storage phosphor from the cassette, transports the storage phosphor along a vertical path where it is read and erased and replaces the storage phosphor in the cassette. An autoloader for such a vertically oriented storage phosphor reader is disclosed in U.S. Pat. No. 5,493,128, issued Feb. 20, 1996, inventor Boutet. The disclosed autoloader is combined with the storage phosphor reader resulting in the need for less floor space for the combined equipment. Moreover, the vertical autoloader automatically handles storage phosphor cassettes of varying sizes without the use of pallets. The vertical autoloader includes a cassette loading station and a cassette unloading station separated by a read site where an exposed storage phosphor is removed from and replaced in the storage phosphor cassette for vertical processing by the storage phosphor reader. Each of the cassette loading and cassette unloading stations includes a plurality of cassette locating slots defined by movable rear and bottom separators and indexers. The operator must load each cassette individually into a loading slot before the next cassette can be loaded. Moreover, the cassette must be loaded with the face oriented 90 degrees from the direction of loading in order to position it correctly into a cassette location slot.
Another generally vertically oriented storage phosphor reader is disclosed in U.S. Pat. No. 4,893,011, issued Jan. 9, 1990, inventors Bauer et al. The disclosed apparatus occupies a large floor area and is not provided with an autoloader to handle multiple cassettes of varying sizes. Moreover, the storage phosphor is removed from the cassette at one location and replaced in the cassette at another location resulting in inefficiencies.
While such systems may have achieved certain degrees of success in their particular applications, there is a need to provide an autoloader for vertically oriented storage phosphor cassettes of varying sizes which is easy to use, which allows the operator to load multiple cassettes at a time without regard to size and which is easily accessible.